public class J01err {
    public static void main(String[] args) {
        System.out.println("耀乐今天很精神");
        Cat c1 = new Cat();
        System.out.println(c1.age);
        c1=null;
//        System.out.println(c1.age);//err
        System.out.println("咏琪回来了！");
    }
}

class Cat{
    int age = 6;
}